The use of lubricants to improve the performance of magnetic recording media, including the dispersion of lubricant in a mixture prior to application of the mixture to a non-magnetic support such as a synthetic resin film, is of course well known, as exemplified by the following.
In U.S. Pat. No. 2,989,415 magnetic recording media includes stearic acid.
U.S. Pat. No. 3,387,993 describes magnetic recording media whose lubricant constituent comprises a mineral lubricating oil and a fatty acid amide, including those amides corresponding to saturated or unsaturated fatty acids having from 6 to 18 carbon atoms. A mixture of 25 parts myristamide and 75 parts stearamide is described. Other suitable amides include caproic, caprylic, lauric, palmitic, mixture thereof, as well as myristic and stearic amides alone or in mixture.
In U.S. Pat. No. 3,492,235 the lubricant is a high molecular weight hydrocarbon containing from about 18 to about 30 carbon atoms, such as squalene, squalane, pristane, eicosane, mixtures thereof, and mixtures of the foregoing with ester lubricants selected from the group stearyl butyrate ester, stearyl stearate ester and stearyl laurate ester.
The use of a monobasic fatty acid having at least four carbon atoms and a melting point lower than 50.degree. C. is described in U.S. Pat. No. 3,833,412. Such acids are said to include caprylic, capric, lauric, linolenic, linolic and oleic acid, with a specific example of stearic acid being given.
U.S. Pat. No. 3,926,826 suggests the use of a stearamide lubricant in magnetic media.
U.S. Pat. No. 3,987,232 suggests the use of a carbonic acid ester lubricant, generally 13 to 33 carbon atoms, in magnetic recording media, and particularly ethyl cetyl carbonate, ethyl laury carbonate, didodecyl carbonate or phenyl cetyl carbonate.
In U.S. Pat. No. 4,152,469 a lubricating film is topically applied to the magnetic film of magnetic recording media. This film is an organic compound such as silicone based chlorosilane, polyethylene, or a stearate such as polyoxyethylene monostearate, morpholino stearate, triethanolamine stearate and mixtures of such materials.
These lubricants have, more particularly, included stearate and fatty ester lubricants.
U.S. Pat. No. 3,274,111 describes magnetic recording media with a self-contained lubricant of a fatty acid ester, or mixture of fatty acid esters, which are mixed with gamma-iron oxide or iron-cobalt-nickel composition. Such solid lubricants are said to have a melting point up to about 40.degree. C. These esters are produced by reaction between a pure monobasic fatty acid or a mixture of two or more monobasic fatty acids containing from about 12 to about 16 carbon atoms and a monohydroxy aliphatic alcohol with from about 3 to 12 carbon atoms. Examples are butyl laurate, an ester prepared from lauryl alcohol and a fatty acid mixture of palmitic acid, a mixture of propyl laurate and butyl myristate, and isobutyl myristate.
U.S. Pat. No. 3,547,693 is one in which magnetic tape incorporates monomeric vinyl stearate, allyl stearate, or other monomeric aliphatic esters of a long chained fatty acid and of an unsaturated alcohol as lubricant. The use of fatty acid esters prepared from a monobasic fatty acid having at least 18 carbon atoms is also recognized. Here the patentee states that the fatty acids should be monomeric, preferably those of stearic acid, such as allyl stearate, vinyl stearate, etc. It is said that the lubricating agent can be incorporated into the magnetic coating at any stage of the coating preparation, including application to the finished coating as by spraying or soaking. The alcohol portion of such lubricants is of low molecular weight, and is of the double-bond unsaturated type.
U.S. Pat. No. 3,630,772 describes a magnetic memory film having incorporated therein a lubricant of a neutral ester of a 2 to 20 carbon dicarboxylic acid with an aliphatic, monofunctional alcohol having 4 to 18 carbon atoms. Such lubricants are diester molecules. The named lubricants include di-n-butylester of adipic acid, didodecylester of adipic acid, didodecylester of succinic acid, di-n-octylester of sebacic acid, and n-butylester of stearyl acid, the latter being a monoester of stearic acid having a 4 carbon alcohol portion.
U.S. Pat. No. 3,704,152 describes a magnetic recording media and recognizes that esters or amines of fatty acids may be added to magnetic layers as lubricants. Stearyl stearate (18 alcohol, 18 acid) is mentioned. Predominately branched fatty acids containing at least 95% by weight of fatty acid having 12 to 18 carbon atoms and at least 40% by weight of branched fatty acids having 18 carbon atoms is suggested as an improved lubricant. Preferred lubricant is methylated fatty acids such as isostearic acid.
U.S. Pat. No. 3,929,659 discloses magnetic recording media with lubricants of low carbon, branched alcohol and 14 carbon acid such as isobutyl myristate, isopropyl myristate, olive oil and stearamide.
Tridecyl stearate in an aqueous mixture with mineral oil has been suggested as a lubricant for extruding nylon fibers (Chemical Abstracts, 1976, volume 84, page 45992), and for various plastic sheets (Chemical Abstracts, 1965, volume 62, page 6650). U.S. Pat. No. 3,834,870 describes the use of tridecyl stearate in the coning of polypropylene yarn to improve color fastness.
An exemplary teaching of lubricants for CrO.sub.2 magnetic recording media is found in U.S. Pat. No. 3,649,541, i.e. lubricants such as amides, alkyl esters, and the metal salts of long-chain fatty acids, hydrocarbyl silicone oils, saturated and unsaturated long-chain hydrocarbons, fluorocarbon telomers, butyl stearate, calcium stearate, stearamide, and squalane.
The foregoing and other features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawing.